CN102035608B - Method for analyzing spatial difference of group path near receiving point - Google Patents
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Abstract
The invention relates to a method for analyzing the spatial difference of group paths near a receiving point, comprising the following nine steps of: firstly, determining latitude, longitude and predicting time of a transmitting point and a receiving point to construct a propagation environment; secondly, calculating a value range of a great-circle distance and a transmitting elevation according to geographic information; thirdly, solving a ray equation to obtain an estimation value of the transmitting elevation; fourthly, calculating a linear interpolation to solve an accurate elevation value; fifthly, expanding the elevation value at an small angle to solve the equation again and process data in order to obtain the distribution of the group paths near the receiving point; sixthly, repeating the steps from the first step to the fifth step to obtain group path distribution at different time; seventhly, obtaining the distribution of the group path difference by time and distance according to the corresponding relation between a receiving position point coordinate and a ray group path; eighthly, calculating the resolution of the group paths and substituting the resolution into a result of the seven step to obtain the change of ground distance resolution delta L with time; and ninthly, averaging the ground distance resolution to obtain the ground distance resolution of a receiver. The invention has a wide application prospect.
Description
(1) technical field
The present invention relates to the method for group path Spatial Difference near a kind of analysis receiving point based on three-dimensional ray tracing technology, belong to New Technology Of Shortwave Communication field.
(2) background technology
In the application of short wave communication, due to by ionospheric electron density influence pockety, causing there is multipath effect, i.e. electric wave respectively along different path arrival receiving points during wave transmissions.In order to ensure in the certain limit of ground, the uniqueness of electric wave group path parameter acquiring reaches the electric wave of receiving point along different paths, it is necessary to distinguish these, and studies the Spatial Difference of the change, i.e. electric wave group path of electric wave ray tracing at diverse location on ground.When the electric wave reflected through ionosphere same layer, which reaches ground, is less than the group path resolution ratio of receiver along the group path difference between two receiving points of transmitter-receiver radial direction, receiver can not tell the change of group path, it is believed that the track indifference of radio wave propagation.If group path difference is more than the group path resolution ratio of receiver, now receiver can tell the change of wave path between two receiving points, it is believed that electric wave track has differences.On the basis of group path resolution ratio, value corresponding on the ground is found, the spatial range resolution of group path just can be obtained.
Currently conventional prediction electrical wave parameters method is mainly the method for channel simulation.Channel simulation method refers to, by carrying out theory analysis to the characteristic of channel, set up channel model, the simulation similar with actual channel is carried out in laboratory environments.This method can simulate boundless region, and climate condition is not limited, and multiplicating experiment can be carried out at any time, and testing expense is few, can shorten the lead time of communication equipment.In various typical short wave channel models, the gloomy model of water (Wattersonmodel) is due to can in most cases simulate the characteristic of short wave channel, and complexity is low, and is recommended and widely used by Consultative Committee on International Radio (CCIR) (CCIR).But the model is limited in that precision is not high, it is necessary to user has certain anticipation and understanding to the ionosphere of specific region and ground magnetic characteristic, operate very inconvenient, and can only realize the simulation to typical environment, universality is not high.
Some characterisitic parameters in short wave communication application are predicted using ray tracing technique, if the model utilized can maximum closing to reality, just can be coincide with actual conditions to a more accurate degree.Ray tracing technique, refers at high frequencies, is approximately ray by electromagnetic wave, and the environmental condition according to where being propagated ray is calculated electromagnetic wave track.Therefore launch point can be just calculated using this technology to all rays of receiving point, and, according to ray tracing, we can calculate all fundamental characteristics (such as receiving point field strength, multidiameter delay, angle of arrival parameter) of every ray, just can therefrom draw the accurate solution of group path.The mainly quasi-parabolic model (QPS) generally used in the application of ray tracing, the model is described below:
General to be referred to as parabolic layer with the layer of the change of height using the simple parabolic curve of form come electron concentration in this approximate layer, its mathematic(al) representation is:
N in formulaemFor electron concentration maximum, hmHeight where when taking maximum for electron concentration, YmFor the half thickness of parabolic layer.Because the mathematic(al) representation is fairly simple, therefore often it is used.
For ray tracing technique, typically all using the form of calculation of two dimension, the situation of display typically only has the great-circle distance for the two places that communicate, therefore, it is simple approximate model in the introducing of ionospheric model and most of the introducing in earth's magnetic field, can only use averaged version in the use of model in addition, it is impossible to so larger in error present on the precision used using environmental model is reconstructed step by step.Under normal conditions one edition do not consider earth's magnetic field influence, but influence of the earth's magnetic field to ray is larger under actual conditions.It is not widely recognized as the basis of ray tracing technique using quasi- parabolic ionospheric model, in addition, during model use, the formal parameter of model, which is obtained, has problem, and ionosphere is continually changing according to time place, and the situation of layering occurs according to local local time, such case is difficult to embody when using quasi-parabolic model, the credibility of model and situation about gearing to actual circumstances are substantially reduced.Geomagnetic Field Model is rarely introduced into general application, and the introducing of Geomagnetic Field Model is seldom explained.In addition, display and calculation using two dimension, the utilizability of the parameter to calculating is not high (angle of arrival of such as ray).So existing technology is calculating accuracy and meeting that actual situation is not high, to the parameter of calculating, further application also is difficult to accomplish.
(3) content of the invention
(1) goal of the invention:It is an object of the invention to provide a kind of method for analyzing group path Spatial Difference near receiving point, it the method overcome the deficiencies in the prior art, on the basis of international reference ionosphere IRI and international Geomagnetic Field Model IGRF, radio wave propagation is emulated using three-dimensional ray tracing technology, obtains more conforming to the data of actual conditions.The Spatial Difference of signal near receiving point is analyzed with reference to emulation data, introduce Rayleigh range resolution ratio and be used as group path resolution criterion, and the concept and computational methods of spatial range resolution are proposed based on group path resolution ratio, the quantitative analysis to Spatial Difference is realized, guidance is provided for the foundation of short wave communication.Therefore, spatial range resolution near the receiving point in short wave communication is predicted based on the ray tracing technique, the application of short wave communication can be instructed.
(2) technical scheme:As shown in figure 1, a kind of method for analyzing group path Spatial Difference near receiving point of the present invention, this method is comprised the following steps that:
Step one:The geographical latitude and longitude coordinates and predicted time of launch point and receiving point are determined, ionospheric electron density distribution and earth magnetism field distribution are built accordingly, and according to magneto-ionic theory, further determine that the spatial distribution of refractive index.
Step 2:According to launch point and the geographical location information of receiving point, the great-circle distance along earth surface between launch point and receiving point, and the possibility span of rough estimate launching elevation can be obtained.
Step 3:For a certain tranmitting frequency, under the ray communication space environment built, solve spherical coordinate system (r, θ,) under ray equation, and to launching elevation carry out linear interpolation calculating.I.e.:In the possibility span at the elevation angle, elevation value is computed repeatedly, until reaching stop value since a certain initial value after calculating every time after 1 ° of increase.
In spherical coordinate system, the form of the writeable component amount of ray equation:
P is group path, kr, kθ,Three components for being wave vector in spherical coordinate system, c is the light velocity, and H is Hamiltonian.H and wave vector k, phase refractive index n relation is:
Step 4:By the calculating of above-mentioned steps three, can obtain ray can just reach the approximate elevation value at receiving point.Under normal conditions, the value is unique, but when ionosphere distribution is relatively uneven, is likely to be obtained multiple elevation values, namely so-called angle of elevation ripple and low angle ripple.Linear interpolation calculating is further carried out to obtained elevation value, relatively accurate elevation value is obtained so that the ray launched at the elevation angle just reaches receiving point.
Step 5:Low-angle extension is carried out to obtained elevation value, ray equation is solved again, is acquired up to the cluster ray tracing near receiving point.Ray data is handled, ray group path and the correspondence mappings of great-circle distance is extracted, linear interpolation calculating is carried out on this basis, the great-circle distance and ray group path information between receiving point neighbouring position point and launch point is obtained.
Step 6:Predicted time is set to different time by repeat step one to step 5, and other conditions are constant.Distribution situation of the group path under different predicted times near receiving point can be obtained.
Step 7:The point centered on receiving point position, the group path at receiving point is defined, can obtain group path difference with the time and the distance away from receiving point distribution, i.e., group path Spatial Difference distribution.
Step 8:In order to further study influence of the Spatial Difference to receiver, receiver ground distance resolution ratio δ L are defined.
According to Rayleigh range resolution ratio formula:δ=c/B, it is assumed that receiver bandwidth is 0.1MHz, radio wave propagation speed is the light velocity, and can obtain group path resolution ratio is:3km.The corresponding ground distance of group path resolution ratio is receiver ground distance resolution ratio δ L.The value is brought into distribution results of the group path difference obtained in step 7 with time and distance, just can obtain corresponding ground distance resolution ratio δ L and change with time.
Step 9:Average is taken to the ground distance resolution ratio under each time, receiver ground distance resolution ratio is finally given.
(3) advantage and effect:
The present invention, with reference to ray communication environments are set up based on IRI, is greatly improved by international ionosphere in accuracy and confidence level.Analysis to group path Spatial Difference near receiving point compensate for current deficiency, can instruct the application of short wave communication.
Using upper, the parameters such as time, antenna directivity when only needing to use transmitting, the corresponding geographical position of receiving point, prediction for user can just dock signal space otherness and radial distance resolution ratio near sink and be predicted, and have larger breakthrough in practicality.Additionally as three-dimensional ray tracing technique, there is larger advantage in terms of visualization, more intuitively use this method.
(4) illustrate
A kind of method flow block diagram for analyzing group path Spatial Difference near receiving point of Fig. 1 present invention
Ionospheric electron density distribution schematic diagram under Fig. 2 certain conditions
Electric wave group path is with time and the change schematic diagram of ground distance when Fig. 3 reflects through E layers
Electric wave group path difference is with time and the change schematic diagram of ground distance difference when Fig. 4 reflects through E layers
Electric wave group path is with time and the change schematic diagram of ground distance when Fig. 5 reflects through F2 layers
Electric wave group path difference is with time and the change schematic diagram of ground distance difference when Fig. 6 reflects through F2 layers
(5) embodiment
See Fig. 1, a kind of method for analyzing group path Spatial Difference near receiving point of the present invention, this method is comprised the following steps that:
Step one:Launch point and receiving point geographical coordinate and predicted time section are determined, the spatial distribution of refractive index is built.
Launch point coordinate setting is in Zhengzhou, and its coordinate is (E113.63 °, N34.80 °), and receiving point coordinate setting is in Qingdao, and its coordinate is (E120.30 °, N36.10 °), and selection predicted time is the 9 of on July 27th, 2009:15.The ray communication environments condition for calculating and obtaining under conditions present is predicted with reference to IGRF using international reference ionosphere IRI and international earth's magnetic field.Two places center is 9:Ionospheric electron density distribution situation when 15, as shown in Figure 2.
Step 2:According to launch point and the geographical location information of receiving point, the great-circle distance along earth surface between launch point and receiving point, and the possibility span of rough estimate launching elevation can be obtained.
Great-circle distance calculation formula is:D=R × φ is wherein:D is great-circle distance, and R is earth radius, is taken as 6370km, and φ is the corresponding radian determined by longitude and latitude, can calculate and obtain D=621.01km.Rough estimate, the elevation angle is between 5 ° to 45 °, in this, as launching elevation scope.
Step 3:Setting tranmitting frequency is 8MHz, under the ray communication space environment built, solves spherical coordinate system (r, θ) under ray equation, and to launching elevation carry out linear interpolation calculating.In spherical coordinate system, the form of the writeable component amount of ray equation:
Wherein P ' is group path, and ordinary circumstance, r is earth radius, and θ is pi/2- geographic latitudes,For geographic logitude (0-360)
β is transmitting inclination angle in formula, and α is transmitting drift angle, and acquisition is specifically calculated by the longitude and latitude of launch point Yu receiving point two places.Kr, k θ,Three components for being wave vector in spherical coordinate system, c is the light velocity, and H is Hamiltonian.H and wave vector k, phase refractive index n relation is:
Wherein, Re is represented and is taken real part;W is angular frequency.
Set initial value be:
It is set in fixed elevation value under 5 °, the initial value of variable is substituted into equation right-hand member, new variate-value is obtained, brings equation right-hand member into again, so circulation, the final ray tracing arrived when the elevation angle is 5 °.Then, elevation value is increased by 1 °, recalculates ray tracing, so circulation is gone down, 45 ° of the maximum until reaching elevation coverage.Obtained ray tracing data are handled, contrasted according to obtained great-circle distance with actual great-circle distance, can judgement reach receiving point, and preserve data.Some numerical results can be obtained as follows:
Sequence number | Tranmitting frequency (MHz) | Launching elevation (degree) | Spherical distance (kilometer) |
1 | 8 | 15.00 | 724.59 |
2 | 8 | 16.00 | 683.39 |
3 | 8 | 17.00 | 650.68 |
4 | 8 | 18.00 | 618.81 |
5 | 8 | 19.00 | 598.34 |
6 | 8 | 20.00 |
580.3 |
7 | 8 | 15.00 | 724.59 |
By being contrasted with actual great-circle distance, it will be seen that receiving point can be reached when the elevation angle is 18 ° or so.
Step 4:Interpolation calculation is further carried out to obtained elevation value, using 0.01 degree as step-length, the calculating process of previous step is repeated, obtains relatively accurate elevation value so that the ray launched at the elevation angle just reaches receiving point.Some numerical results are as follows:
Sequence number | Tranmitting frequency (MHz) | Launching elevation (degree) | Spherical distance (kilometer) | Sequence number | Tranmitting frequency (MHz) | Launching elevation (degree) | Spherical distance (kilometer) |
1 | 8 | 17.89 | 623.09 | 6 | 8 | 17.94 | 621.61 |
2 | 8 | 17.90 | 622.49 | 7 | 8 | 17.95 | 621.29 |
3 | 8 | 17.91 | 622.55 | 8 | 8 | 17.96 | 621.03 |
4 | 8 | 17.92 | 622.14 | 9 | 8 | 17.97 | 620.85 |
5 | 8 | 17.93 | 621.92 | 10 | 8 | 17.98 | 620.44 |
It can obtain reaching receiving point just when the elevation angle is 17.96 ° by calculating us.
Step 5:Low-angle extension is carried out to obtained accurate elevation value, ray equation is solved again, is acquired up to the cluster ray tracing near receiving point.Ray data is handled, ray group path and the correspondence mappings of great-circle distance is extracted, linear interpolation calculating is carried out on this basis, the great-circle distance and ray group path information between receiving point neighbouring position point and launch point is obtained.Here we are from 16.96 ° to 18.96 °, with 0.01 ° for step-length, and the relation that equation obtains group path and great circle is solved again, as shown in the table:(only providing preceding 40 groups of data here)
Sequence number | Tranmitting frequency | Launching elevation | Group path | Spherical distance | Sequence number | Tranmitting frequency | Launching elevation | Group path |
|
1 | 8.00 | 17.76 | 673.78 | 627.36 | 21 | 8.00 | 17.97 | 667.58 | 620.85 |
2 | 8.00 | 17.77 | 673.68 | 627.23 | 22 | 8.00 | 17.98 | 667.38 | 620.63 |
3 | 8.00 | 17.78 | 673.18 | 626.73 | 23 | 8.00 | 17.99 | 667.08 | 620.31 |
4 | 8.00 | 17.79 | 672.78 | 626.33 | 24 | 8.00 | 18.00 | 666.88 | 620.09 |
5 | 8.00 | 17.80 | 672.48 | 626.01 | 25 | 8.00 | 18.01 | 666.48 | 619.68 |
6 | 8.00 | 17.81 | 672.18 | 625.70 | 26 | 8.00 | 18.02 | 666.48 | 619.65 |
7 | 8.00 | 17.82 | 671.68 | 625.20 | 27 | 8.00 | 18.03 | 666.08 | 619.24 |
8 | 8.00 | 17.83 | 671.18 | 624.69 | 28 | 8.00 | 18.04 | 665.88 | 619.02 |
9 | 8.00 | 17.84 | 671.18 | 624.66 | 29 | 8.00 | 18.05 | 684.38 | 636.25 |
10 | 8.00 | 17.85 | 671.18 | 624.63 | 30 | 8.00 | 18.06 | 665.58 | 618.67 |
11 | 8.00 | 17.86 | 670.68 | 624.12 | 31 | 8.00 | 18.07 | 665.38 | 618.45 |
12 | 8.00 | 17.87 | 670.08 | 623.53 | 32 | 8.00 | 18.08 | 665.18 | 618.23 |
13 | 8.00 | 17.88 | 669.78 | 623.21 | 33 | 8.00 | 18.09 | 664.48 | 617.56 |
14 | 8.00 | 17.89 | 669.68 | 623.09 | 34 | 8.00 | 18.10 | 664.08 | 617.17 |
15 | 8.00 | 17.90 | 669.08 | 622.49 | 35 | 8.00 | 18.11 | 698.18 | 649.05 |
16 | 8.00 | 17.91 | 669.18 | 622.55 | 36 | 8.00 | 18.12 | 663.68 | 616.76 |
17 | 8.00 | 17.92 | 668.78 | 622.14 | 37 | 8.00 | 18.13 | 663.29 | 616.37 |
18 | 8.00 | 17.93 | 668.48 | 621.83 | 38 | 8.00 | 18.14 | 663.09 | 616.16 |
19 | 8.00 | 17.94 | 668.28 | 621.61 | 39 | 8.00 | 18.15 | 662.69 | 615.77 |
20 | 8.00 | 17.95 | 667.88 | 621.19 | 40 | 8.00 | 18.16 | 662.49 | 615.57 |
Step 6:Repeat step one will be respectively set to 10: 15,11: 15,12: 15,13: 15,14: 15,15: 15 and 16: 15 the time, other parameters are constant to step 5.
Step 7:According to point coordinates near receiving position and the corresponding relation of ray group path, using above-mentioned simulation result, the group path near a little is can be received with the distribution away from discrete time.According to the difference in reflecting layer, distribution situation during E layers and F2 layers reflection is considered respectively, as shown in Figure 3 and Figure 4.Further, on the basis of the group path at receiving point, distribution of the group path difference with time and distance can be obtained, as shown in Figure 5 and Figure 6.
Step 8:In order to further study influence of the Spatial Difference to receiver, receiver ground distance resolution ratio δ L are defined.
According to Rayleigh range resolution ratio formula:δ=c/B, it is assumed that receiver bandwidth is 0.1MHz, radio wave propagation speed is the light velocity, and can obtain group path resolution ratio is:3km.The corresponding ground distance of group path resolution ratio is receiver ground distance resolution ratio δ L.Group path resolution ratio is brought into distribution results of the group path difference obtained in step 7 with time and distance, corresponding ground distance resolution ratio δ L change with time when just can respectively obtain E layers and F2 layers reflection, as shown in the table:
Step 9:It can see in table, within the selected period, ground distance resolution ratio during E layers of reflection is:Ground distance resolution ratio when 3.20km, F2 reflect is 6.15km.Here, ground distance resolution ratio 3.20km during E layers of reflection is represented:For same emitting radio waves, assuming that the receiver of receiving point is main receiver, the receiver at neighbouring another point is secondary receiver, when the distance between major-minor receiver is less than 3.20km, two receivers can not tell the difference of received electric wave, it is believed that it is identical to receive electric wave.It is similar when 6.15km implication is with E layers of reflection when being reflected for F2 layers.
Claims (1)
1. a kind of method for analyzing group path Spatial Difference near receiving point, it is characterised in that:This method is comprised the following steps that:
Step one:The geographical latitude and longitude coordinates and predicted time of launch point and receiving point are determined, ionospheric electron density distribution and earth magnetism field distribution are built accordingly, and according to magneto-ionic theory, further determine that the spatial distribution of refractive index;
Step 2:According to launch point and the geographical location information of receiving point, the great-circle distance along earth surface between launch point and receiving point, and the span of rough estimate launching elevation are obtained;
Step 3:For a certain tranmitting frequency, under the ray communication space environment built, spherical coordinate system is solved(r、θ、)Under ray equation, and to launching elevation carry out linear interpolation calculating;I.e.:In the span at the elevation angle, elevation value is since a certain initial value, and 1 ° of increase is computed repeatedly after calculating every time, until reaching stop value;
In spherical coordinate system, ray equation is write as the form of component:
P' is group path, kr, kθ,Three components for being wave vector in spherical coordinate system, c is the light velocity, and H is Hamiltonian;H and wave vector k, phase refractive index n relation is:
Step 4:By the calculating of step 3, the approximate elevation value at receiving point can just be reached by obtaining ray;Under normal conditions, the value is unique, but when ionosphere distribution is relatively uneven, obtains multiple elevation values, namely so-called angle of elevation ripple and low angle ripple;Interpolation calculation is further carried out to obtained elevation value, relatively accurate elevation value is obtained so that the ray launched at the elevation angle just reaches receiving point;
Step 5:Low-angle extension is carried out to obtained elevation value, ray equation is solved again, is acquired up to the cluster ray tracing near receiving point;Ray data is handled, ray group path and the correspondence mappings of great-circle distance is extracted, linear interpolation calculating is carried out on this basis, the great-circle distance and ray group path information between receiving point neighbouring position point and launch point is obtained;
Step 6:Predicted time is set to different time by repeat step one to step 5, and other conditions are constant;Obtain distribution situation of the group path under different predicted times near receiving point;
Step 7:The point centered on receiving point position, on the basis of the group path at receiving point, obtain group path difference with the time and the distance away from receiving point distribution;
Step 8:According to Rayleigh range resolution ratio formula:δ=cB, if it is 0.1MHz that receiver bandwidth, which is B, radio wave propagation speed is the light velocity, and obtaining group path resolution ratio is:3km;The value is updated in distribution results of the group path difference obtained in step 7 with time and distance, obtains corresponding ground distance resolution ratio δ L and change with time;
Step 9:Average is taken to the ground distance resolution ratio under each time, receiver ground distance resolution ratio is finally given.
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